Systems that generate multiple coherent phase output are useful in a number of applications. One exemplary useful application is in signal modulation.
Modulation types currently used in digital communication systems include amplitude modulation, frequency modulation and phase modulation. The phase modulation type, that is, a phase shift keying (PSK) type, is the signal modulation technology currently adopted in most mobile communication systems.
The simplest PSK signal is the linear or binary PSK signal. In this case, the carrier phase is shifted between two possible states, 0 degree (bit “0”) and 180 degrees (bit “1”). In a quadrature PSK scheme, four logic bits can be coded by 0 degree, 90 degrees, 180 degrees, and 270 degrees.
Current PSK transmitters involve an oscillator to generate the carrier signal and a delay to shift the signal phase for another output with a different phase. These transmitters often include complex circuitry that is difficult to scale down to very small dimensions.